convexity of the posterior lobe, give that end a narrow 
contour. The striae are obtuse ridges coinciding with 
the lines of growth ; they are smooth. 
Miss E. Hill, whose kindness I have often had occa- 
sion to acknowledge, sent me this shell from Pickeridge 
Hill, near Roundsford Park, Taunton. It is found in a 
grey argillacious Limestone, that is in some parts so soft 
and loose that the shells may be picked out of it with ease ; 
in other parts the stone is firm, and the shell adheres 
strongly to it, in which case the surface of the shell that 
is exposed by fracture has a glistening velvety lustre, 
arising from its crystalline structure. The specimens 
are frequently narrower than the figure. 
MOBIOLA aspera. 
TAB, CCXII.— Fig. 4. 
Spec. Char. Ovate, elongated, posteriorly pointed; 
very gibbose, longitudinally striated ; strise 
elevated, rough, very numerous ; posterior 
lobe obscure, wrinkled, small. 
*1 he small and nearly fiat posterior lobe leaves the beaked 
end of this Modiola so small as to give it much of the 
contour of a Mytillus. The depth of the two valves to- 
gether is greater than the width, and the length is twice 
the depth. The roughness of the striae proceeds from 
minute elevated scales, that are most conspicuous near 
the margin of the shell, and are nearly obliterated to- 
wards the beaks. 
For this beautiful shell I am indebted to Mr. Goodhall, 
who brought it from a pit in Gregory’s Land, at F elmar- 
sham, near Bedford. 
